49ers’ run defense threatening NFL record

After nine games, San Francisco is the only NFL team to not allow a rushing touchdown and it could establish an NFL record for the fewest rushing touchdowns allowed in a season.

Since the NFL adopted a 16-game regular season in 1978, the fewest touchdowns allowed on the ground in a season is four. That record is held by 11 teams and it was done most recently by the 2008 Ravens.

The all-time NFL record for the fewest rushing touchdowns allowed in a season is two – a mark held by the Vikings (1971), Cowboys (1968) and Lions (1934).

The Niners haven’t allowed a rushing touchdown in their past 10 games dating back to last season. The franchise record of 13 games was set during the 1985 and ’86 seasons.

Other notes:

* Running backs have 42 yards on 20 carries (2.1 yards a carry) against the 49ers in the red zone this season.

* St. Louis’ Steven Jackson was the last player with a rushing touchdown against the Niners. Jackson had a one-yard scoring run in the first quarter of the Rams’ 25-17 win on Dec. 26, 2010.

* In their past 19 games, the Niners have allowed five rushing touchdowns.